1. Technical Field
The present invention relates to a method of transmitting messages via a mobile communications network. More particularly, but not exclusively, the invention relates to methods of transmitting SMS text messages of the GSM system in a secure way.
2. Related Art
For mobile communication device users, SMS text messages provide a quick, convenient method of sending and receiving messages. Messages are transmitted via a messaging centre. If messages cannot be delivered to the mobile terminal, they are stored at the messaging centre until they can be delivered. However, it may happen that messages eventually ‘time-out’ without warning.
SMS also provides a rarely used option to send ‘flash messages’, which appear immediately on the device, without requiring user interaction to read them. The SMS standard also supports e-mail (via X-400 protocols) and both binary and text based data.
The conventional short messaging like the SMS service in GSM systems has the drawback that the service is unsuitable for many applications, such as electronic commerce or other applications where a secure and controlled data delivery is required. Below, we set out some reasons why the conventional short messaging is unsuitable for secure data delivery.
Firstly, the sender of a message is usually not informed whether the message has been delivered to the receiving mobile terminal and has been received by the user. The GSM system provides also for acknowledged messaging, wherein an acknowledgment is transmitted to the sender of the message as soon as the message is delivered to the messaging centre. However, the sender cannot know whether the message reached the mobile terminal and, more particularly, whether the message actually reached the user for whom the message was intended.
Secondly, data transmitted via SMS may be decoded by third parties with a suitable digital receiver. Moreover, the messages are usually stored in the mobile terminal's memory. Thus any third party gaining access to the terminal may read the messages.
Thirdly, the user of a mobile terminal cannot necessarily be identified in many cases. Especially by transmitting a SMS message via the Internet or other delivery mechanisms, the identity of the sender of the message may be concealed to the receiving user, or the recipient of the message may not be that intended by the sender.